A pressure sensor module of the above-mentioned type is known from WO2002/079742. The known pressure sensor module is used in a gauge differential pressure configuration. Two identical sensor sensors modules are used to measure the pressure of two media. Each configuration comprises a hole. The hole passes through a substrate which is covered at one side by the sensing element. The other sides of both sensing elements see the same reference pressure, typically atmospheric pressure, due to the fact that they sit in the same chamber. An additional inlet can pass through the housing of the pressure sensor to provide atmospheric pressure to the chamber. In this open configuration, water vapor and other contaminants can freely enter the chamber.
The pressure media, designated as a low and a high pressure, enter the housing through separate pressure inlets and act upon the sensing elements via the hole through the substrate.
Furthermore, similar pressure sensors modules are known wherein the hole through the substrate is filled with an acid resistant gel to isolate the sensing element from contaminants and the acidic environment.
The through hole can be made with laser cutting. Laser cutting of through holes in ceramics is an economical process commonly implemented in hybrid electronics. However, the laser cutting process can damage the inherent acid robustness of the ceramic by creating micro cracks and/or forming more vulnerable phases of the ceramic (i.e. glassy phase) on the surface of the ceramic. When used in an acidic environment, such as diesel exhaust, the untreated laser cut surface may be prone to chemical attack and corrosion. This laser cut surface may be prone to chemical attack and corrosion even when the through holes are potted with a protective coating. This chemical attack and corrosion will change the properties of the protective coating which could result in malfunctioning of the pressure sensor.